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1. Field of the Invention
The invention is related to the field of communication systems, and in particular, to a hybrid fiber wireless communication system that transfers Radio Frequency (RF) signals.
2. Description of the Prior Art
Baseband data services that carry voice, video, and data are experiencing strong growth. Some examples of baseband data services include Asynchronous Transfer Mode (ATM), Internet Protocol (IP), Code Division Multiple Access (CDMA), and Time Division Multiplex (TDM). Baseband data services are provided by systems such as ATM switches, IP routers, and Synchronous Optical Network (SONET) multiplexers.
Wireless services that carry voice, video, and data are also experiencing enormous growth. Some examples of wireless services include Microwave Multi-point Distribution System (MMDS), Local Multi-point Distribution System (LMDS), Personal Communications Services (PCS), and the use of unlicensed spectrum. These wireless services use signals in the RF range. To convert baseband data into RF data, the baseband data is modulated with a carrier frequency to up-convert the baseband data into the RF range.
Wireless communication systems often use a fiber network to transfer data from wireless base stations to land-based networks. When the wireless communication system offers baseband data services, the base stations require baseband equipment, such as ATM switches, IP routers, and Synchronous Optical Network (SONET) multiplexers. As baseband data services grow, so does the cost and complexity of the baseband data equipment in the base stations.
Base stations often face severe floor space restrictions, and baseband data equipment takes up valuable space. The baseband data equipment also requires increased power and security. More importantly, the base stations require skilled data technicians to test and maintain the baseband data systems. Baseband data technicians typically require more training and compensation than RF technicians. Inevitably, expensive and complex baseband data equipment is under-utilized in some base stations. This represents a tremendous waste of baseband data equipment and technicians.
Hybrid Fiber Coax (HFC) communication systems were developed in the 1980""s to deliver broadband video to residential areas. In a typical HFC system, a central node converts analog and digital video to optical RF signals. A fiber network then distributes the optical RF signals from the central node to various fiber optic nodes in the residential area. The fiber optic nodes convert the optical RF signals to electronic RF signals. Coaxial cable then transfers the electronic RF signals to the residences. Unfortunately, the coaxial cable place a bandwidth limitation on the system at less than 900 MHz. In addition, HFC systems were designed for broadcast video services and not for a continually changing group of wireless services.
The invention solves the above problems with a Hybrid Fiber Wireless (HFW) communication system performs baseband data processing and provides multiple wireless services. The HFW system has greater bandwidth than prior hybrid fiber coax systems. The hybrid fiber system is cheaper and less complex than other wireless communication systems that perform baseband data processing.
Advantageously, baseband data equipment is concentrated in a central service node that exchanges optical RF data with the base stations. The optical RF data is exchanged using multiple add-drop points. The communication path between the central service node and the customer premise equipment uses mainly passive components. Thus, the base stations are greatly simplified to save maintenance costs and floor space. The concentration of baseband equipment in a central service node allows for more efficient utilization of equipment, support systems, and data technicians. For example, base stations would need less floor space, power, and air conditioning.
The HFW communication system comprises a central service node, a plurality of base stations, and a fiber network. The central service node is configured with a baseband data system, a central RF system, and a central optical system. The base stations are each configured with a base station optical system, a base station RF system, and a base station transceiver system. These systems are configured to operate as follows.
The baseband data system in the central service node processes baseband data. The central RF system up-converts the baseband data into electronic RF data. The central optical system converts the electronic RF data into optical RF data. The fiber network exchanges the optical RF data between the central service node and the base stations. The base station optical system converts the optical RF data into the electronic RF data. The base station RF system modifies frequencies of the electronic RF data. The base station transceiver system converts the electronic RF data into wireless RF data and exchanges the wireless RF data over an air interface with customer premise equipment.